Since the first systematic study of dielectric resonator antennas (DRAs) in 1983 (LONG, S. A., McALLISTER, M. W., and SHEN, L. C.: ‘The resonant cylindrical dielectric cavity antenna’, IEEE Trans. Antennas Propagat., AP-31, 1983, pp 406-412), interest has grown in their radiation patterns because of their high radiation efficiency, good match to most commonly used transmission lines and their small physical size (MONGIA, R. K. and BHARTIA, P.: ‘Dielectric resonator antennas—A review and general design relations for resonant frequency and bandwidth’, Int. J. Microwave & Millimeter Wave Computer-Aided Engineering, 1994, 4, (3), pp 230-247). Most configurations reported have used a slab of dielectric material mounted on a ground plane excited by either an aperture feed in the ground plane or by a probe inserted into the dielectric material. A few publications have reported on experiments using two probes fed simultaneously in a circular dielectric slab. These probes were installed on radials at 90° to each other and fed in anti-phase so as to create circular polarisation (MONGIA, R. K., ITTIPIBOON, A., CUHACI, M. and ROSCOE D.: ‘Circular polarised dielectric resonator antenna’, Electron. Lett., 1994, 30, (17), pp 1361-1362; and DROSSOS, G., WU, Z. and DAVIS, L. E.: ‘Circular polarised cylindrical dielectric resonator antenna’, Electron. Lett., 1996, 32, (4), pp 281-283.3, 4) and one publication included the concept of switching probes on and off (DROSSOS, G., WU, Z. and DAVIS, L. E.: ‘Switchable cylindrical dielectric resonator antenna’, Electron. Lett., 1996, 32, (10), pp 862-864).
All references mentioned herein are incorporated herein by reference: